The present invention pertains to an instrument for protecting the corneal endothelium of the eye during cataract extraction by the small incision technique, commonly known as the Phacoemulsification or Phaco technique.
In recent years, two surgical techniques for removing a cataract from the eye are employed. The large incision technique and the small incision or Phaco technique.
In the large incision technique, a large incision (approximately 8-10 mm) almost half the circumference of the cornea is made, and the cataract is expressed or squeezed out of the eye manually. The advantage with this technique is that it is much easier to perform. The disadvantages are the longer time to recuperate and it also creates more astigmatism.
In the small incision or Phaco technique, a small incision, approximately 3 mm long is made on the superior margin of the cornea. An ultrasonic cutting tip is then inserted inside the eye to remove the cataract. The advantages with this technique are the stronger wound, faster recuperation, and less astigmatism. The main disadvantage is that it is more difficult to perform.
There are two main problems with the Phaco technique, the first problem is the danger of rupturing the lens posterior capsule. The second problem is the risk of damaging the corneal endothelium.
The present invention deals exclusively with the second problem, namely with providing protection of the corneal endothelium during Phacoemulsification.
A brief description of the anatomy of the eye is in order, here made with reference to FIG. 1. The front part of the eyeball is a clear transparent structure called the cornea 10. The back surface of the cornea 10 is lined with a single layer of very delicate non-regenerating cells called the endothelium 12. The endothelium 12 keeps the cornea 10 transparent. When a large area of the endothelium 12 is damaged, as during cataract surgery, the cornea 10 swells up and becomes cloudy or opaque. Seeing through a cloudy cornea is like seeing through a foggy or frosted windshield of a car, and hence vision is very poor.
Posterior to the cornea 10 is the iris 16, the colored part of the eye (brown, blue or green eyes). The opening in the enter of the iris is the pupil 14.
Behind the iris is the lens 18 of the eye. A normal lens is clear and transparent. When the lens 18 becomes cloudy or opaque, as in old age, it is called a cataract. In surgery, the cloudy cataract is removed and replaced with a clear artificial lens called an intraocular lens implant.
During surgery using the Phaco technique, the cataract nucleus 18A tends to float up and come in contact with the corneal endothelium, as it is being removed with the ultrasonic cutting tip 20 (FIG. 8). Everytime the cataract nucleus touches the delicate endothelium, it destroys some endothelial cells. When damage to the endothelium 12 is extensive, the cornea 10 becomes permanently cloudy. The eye will not have good, useful vision. The operation is a failure and additional surgery, i.e., a corneal transplant, is needed later.
The object of the present invention is to protect the endothelium from contact with the cataract nucleus 18A during Phaco technique surgery.